1. Field of the Invention
The present invention relates in general to bumpers for a motor vehicle, and more particularly to bumpers of a type which can serve as a so-called dynamic damper.
2. Description of the Prior Art
Nowadays, some of wheeled motor vehicles are equipped with a bumper of so-called dynamic damper type in order to reduce unpleasant vibration of the vehicle body caused by engine operation particularly at idling. In such bumper, the weight of the same is use as a damping mass. One of the conventional bumpers of such type is disclosed in Japanese Utility Model Provisional publication No. 60-112736, which, as shown in FIGS. 2 and 3 of the attached drawings, uses both a bumper facia A and an armature B, which have considerable weights, as a damping mass. For this, bumper stays C are secured to laterally spaced rigid portions of the vehicle body, and supporting brackets D are secured to leading ends of the bumper stays C respectively. Each bracket D has upper and lower walls between which an inboard part of the armature B is spacedly received. Between each wall of the bracket D and the armature B, there is arranged a bushing-mounted holder E1 or E2 for elastically holding the armature B to the bracket D. Each holder E1 or E2 comprises a bushing mounted to the associated wall of the bracket D and a set of bolt and nut for connecting the bushing to the armature B. The bumper facia A covers an outboard part of the armature and is secured to the same by means of upper and lower brackets secured thereto. Although not shown in the drawing, the armature B has suitable portions which are secured to the bumper stays C directly.
With the construction as described hereinabove, it will be appreciated that the bumper facia A and the armature 8 constitute an integrated unit which has a specific vibration mode different from that of the vehicle body, because the unit is supported by the vehicle body through the bushing-mounted holders E1 and E2. Thus, the unpleasant vibration of the vehicle body at idling is suppressed or at least damped.
However, in the conventional bumpers of the abovementioned type suffer from the following drawbacks because of the inherency in construction.
That is, because the unit of the bumper facia A and the armature 8 vibrates at its specific frequency different from that of the vehicle body, the vibration of the bumper facia A is clearly observed. This tends to provide the observers with unpleasant feeling.
Furthermore, since the bumper facia A vibrates freely relative to the vehicle body, it is necessary to provide a considerable clearance H between the bumper facia A (viz., an upper surface of the same, see FIG. 2) and a lower part (viz., a front lower part F of an engine hood) of the vehicle body. The provision of such clearance H deteriorates external view of the vehicle.